Electrical furnace for treating highly-refractory substances.



i l l Nd. 704,649. Patented July I5, I902" H. MAXIM.

ELECTRICAL FURNACE FOR TREATING HIGHLY REFRACTORY SUBSTANCES.

(Application filed on. so, 1901..

(No Model.)

19% hwooeo I A M A THE Noam PETERS co FHOTO-LIYHO, \A'ASHINGTON, n. c.

UNTTED STATES PATENT OFFICE.

HUDSON MAXIM, OF BROOKLYN, NETV YORK.

ELECTRICAL FURNACE FOR TREATING HIGHLY-REFRACTORY SUBSTANCES.

SPECIFICATION forming part of Letters Patent No. 704,649, dated. July15, 1902.

Original application filed June 25,1895, Serial No. 553,952. No. 80,532.

To U/ZZ whom, it may concern:

Be it known that I, HUDsoN MAXIM, a resident of Brooklyn, New York, haveinvented a new and useful Improvement in Electrical Furnaces forTreating Highly Refractory Substances, whichinvention is fully set forthin the following specification.

In myapplication, Serial No. 553,952, filed June 25, 1895, of which thepresent application is a division,I have described and claimed a processof making calcium carbid.

The present invention relates to electrical furnaces, and has for itsobject to provide a furnace of this class adapted to successfully andcontinuously treat highly-refractory substances requiring for theirtreatment a constant very high ten peratu reas,for example, lime andcarbon in the manufacture of calcium carbid. In the treatment of suchmaterials the constant very high temperature required results indestructive wear and tear on the furnace; and one of the objects of thisinvention is to obviate such destructive action, as well as provideagainstinjury to the materials under treatment.

With these objects in view the invention consists in a revolubleelectric furnace through which the material to be treated is advanced ina continuously-moving stream and subjected to a progressively-increasingtemperature from the point of entrance to the furnace to its point ofexit therefrom. As a preferred means of securing this result I providethe revoluble furnace with an interior electric conductornvhich isadapted to receive independent electric currents from a series of outerelectrodes disposed at successivelyadvancing points along the furnace,each successive and additional electric current reaching the interiorconductor from the successive outer electrodes adding quantity to thecurrent already flowing through the common interior conductor, therebygenerating an intense heat, increasing in degree toward the place ofdischarge of the material to be treated.

In some cases, as in the manufacture of calcium carbid, the materialunder treatment may be of sufficient conductivity to serve as theinterior conductor of the electric current employed.

Divided and this application filed October 30, 1901. Serial (No model.)

The inventive idea involved may receive various mechanical expressions,and for the purpose of illustrating the invention I have shown one ofthese in the-accompanying drawings; but it is to be understood that suchdrawings are for the purpose of illustration only, and not as confiningthe invention to the specific construction shown.

In said drawings, Figure 1 is a longitudinal sectional viewof one styleof horizontal furnace apparatus; and Fig. 2 is a transverse sectionthereof, taken on the lineccmin Fig. 1.

The numeral 1 indicates the furnace body or shell, which is preferablymade of steel and may have a fire-clay or other refractory electricallynon-conductive lining2, within which is a centrifugally-maintainedauxiliary protective lining or bed 3, hereinafter more fully'described.The material 4 under treatvmentis fed to the furnace in any suitableway,

as from a hopper by a screw conveyer 5, and fiows through or along 011the bed 3 and discharges at the opposite end into a chute 6, which mayconvey the treated material to any suitable receiver. Opposite heads 78, with interposed insulation 9, of asbestos or other suitable material,are bolted to the ends of the furnace-body. Thehead 7 has an openingreceiving the material feed-spout, and the head 8 has a central openingfor discharge of the treated material and is preferably flared outwardand faced by insulation 10, preferably magnesite. The head 8 also has aflange 11, which projects inward inside of the fireclay lining 2 andinto the auxiliary protective bed 3 to allow the electric current to betaken off from the bed through the head.

The electric appliances furnishing the progressively-increasingtemperature in this apparatus comprise, in connection with the interiorprotective bed 3, a series of outer circumferential electrodes 12,preferably arranged in two opposing radial pairs or in series of four inthe same transverse plane and projecting inward to the protective bed totransmit thereto electric current, which usually fuses the bed materialto a fluid state, while it is maintained in tubular form by centrifugalforce. For each transverse or circumferential series of electrodes 12,and preferably over an interposed encir" cling asbestos packing 13,there is shrunk around the steel furnace-body a metal ring or band 13,which for each electrode has a cup-shaped radial projection 14. Insideof each cup 1 1- a shoulderedinsulation 15 is litted to the furnace-body1 and its lining 2. The electrode is passed into the cup 1 1 and restsby its shoulder on a shoulder of the insulation 15. A suitably-insulatedannular packing 16 is placed on the outer end of the electrode, aroundits outwardly-projecting stem 17, which preferably enters an opening ina conductive plug 18, screwed into the cup let to retain the electrode.Centrifugal force developed by rotation of the furnace throws theelectrode 12 outward and compresses the packing 16 between it and theplug to prevent leakage past the electrode of the fluid-bed 3 or thefused materials under treatment in the furnace.

The electrode-retaining plugs 18 of each circumferential series are eachin contact with an independent conductive segment 19 of a ring which mayhave as many segments as there are electrodes in the series, thesegments being preferably separated by end insulation 20, thus directingthe current toward the electrodes in contact with the respectivesegments. The ring may be removed to allow the plugs to be taken out togive access to the electrodes and their packings. Each of the uppermostsegments 19 in Fig. 2 is in circuit by a brush 21 with one pole of adynamo 22, while the two lower segments receive current from separatedynamos 23 through wires leading to the axis of the antifriction-rollers24, on which the furnace rests for rotation at any required speed by oneor more pinions 25, meshing with a toothed gear 26 on the furnace-body.Wires 27 connect a conductive rod 28 with each of the dynamos 22 23 toreceive the return current by means of a brush 29 on the rod bearing onthe head 8 of therotating furnace-body. There being four currentstransmitted to each circumferential series of electrodes 12, the furnaceshown in Figs. 1 and 2 and having five such series will have twentyindependent electric currents supplied to it, and it may be by as manyseparate dynamos, to give their joint powerful heating effect on thematerial under treatment. It will be noticed that by providing thering13 with projecting cups 14 and fitting the conductive segments 19outside of these cups or the plugs 18 in them considerable space isprovided at 30 for circulation of air inside and quite around the parts19 to prevent overheating of the exterior contacts by either theelectric currents which they distribute to the furnace or the heatgenerated by said currents within the furnace and radiating through itsbody-wall.

The operation of this apparatus is as follows: Before feeding thematerial 4 to be treated into the furnace any suitable substance orcompound having proper electrical resistance and a specific gravityhigher than that of the material to be treated may be charged into therotating furnace upon its lining 2 and be melted to form the auxiliaryprotective fluid bath or bed 3 by dynamos 22 23. The fused material ofthe bed 3 forms a common interior electrode, along which returns theconstantly-increasing electric current derived from the successivecircumferential series of electrodes 12, and whereby a very hightemperature is obtained in the furnace, due mainly to therapidly-increasing supply of electric current entering the fluidbedtoward the discharge end of the furnace and the resultant heating of thebed incidental to the resistance offered by the bed to the passage ofthe com mon return-current. The fluidbed is maintained in tubular formagainst the furnace-lining 2 by centrifugal force, which also willmaintain the lining 2 in tubular form against the furnace body or shellshould this lining become softened or partly fused by the intense heatattained within the furnace. As the material 4 is fed into the furnaceby the screw 5 or otherwise the centrifugal force causes the material toassume a tubular form and to float or drift forward easily along thetubular fluid-bed 3 while subjected to the intense heat of the electriccurrent derived from the circumferential electrodes 12 and returningthrough the fluidbed. The electrothermal treatment may continue for alonger or shorter time, as determined by the rapidity of feed of thematerial or the speed of rotation of the furnace or the nature of thematerial. The treated material discharges from the furnace into thereceiver 6. In treating certain classes of ma terials the fluid-bed 3serves a very important function by constituting a practicallyfrictionless tubular bearing-surface, along and within which the treatedmaterials are carried, floated, or drifted forward through the furnaceby the developed centrifugal force aided by the natural tendency of themate rials to seek their own level.

It will be understood that the fluid-bed 3 may be formed or built upfrom and be constantly renewed by a portion of the materials undertreatment or from one of the products of the reaction effected in thefurnace. One such material is calcium carbid, to produce which calciumoxid and carbon are fed into the furnace and subjected to its heatenergy. As the reaction takes place and the carbid is formed it iscarried by centrifugal force against the lining 2 of the furnace-body toform an incandescent auxiliary protective lining 8 therefor, and thesurplus carbid will discharge from the furnace into the receiver 6, thefluid-bed or protective lining being constantly renewed byfreshly-formed carbid on its way to the outlet.

At various stages of the operation Water or other cooling fluid will bethrown over the exterior walls of the furnace from a series of IIOvoacee nozzles 60, Fig. 2, or equivalent cooling apparatus to preventoverheating of the furnace.

"What is claimed is 1. In an electrical apparatus for making calciumcarbid, an electrical circuit, a carbid conductor included in saidcircuit, whereby said conductor is maintained incandescent, meansdelivering carbid-forming materials to the heating-field, and meansuninterruptedly moving the calcium carbid from the heating field as fastas formed.

2. In an electrical apparatus, for making calcium carbid, an electriccircuit, a carbid conductor included in said circuit, whereby saidconductor is maintained incandescent, and means moving the calciumcarbid from the heating-field as fast as formed.

3. In an electrical apparatus for making calcium carbid, an electriccircuit, a carbid conductor included in said circuit, whereby saidconductor is maintained incandescent, and means continuously moving thecalcium carbid from the heating-field as fast as formed.

4. In an electrical apparatus for making calcium carbid, an electriccircuit, a carbid conductor included in said circuit, whereby saidconductor is maintained incandescent, means moving the calcium carbidfrom the heating-field as fast as formed, and means supplyingcarbid-forming materials to the heating-field.

5. In an electrical apparatus for making calcium carbid, an electriccircuit, a carbid conductor included between opposed electrodes in saidcircuit, whereby said conductor is maintained incandescent, and meansmov ing the calcium carbid from the heating-field as fast as formed,thereby maintaining the electrical resistance between the electrodesapproximately uniform.

6. An electrical apparatus for making calcium carbid provided with aninlet for the carbid-forming materials and an outlet-for the calciumcarbid when formed, an electric circuit, a carbid conductor included insaid circuit, and means continuously moving the calcium carbid from theheating-field to the outlet as formed.

7. In a rotatable electrical apparatus for making calcium carbid, anelectric circuit, a carbid conductor included in said circuit, and meansrotating the apparatus and removing the calcium carbid as formed fromthe heating-field of the apparatus.

8. In a rotatable electrical apparatus for making calcium carbid, anelectric circuit, a carbid conductor included in said circuit, and meanscontinuously rotating the apparatus and thereby continuously removingthe calcium carbid from the heating-field of the apparatus as formed.

9. In an electrical apparatus for making calcium carbid, a carbidconductor, a plurality of electric circuits in each of which saidconductor enters as an element, and means for moving the calcium carbidfrom the furnace as formed.

10. Apparatus for electrothermally treating materials, comprising arevoluble struc ture having peripheral electrodes, retainerstherefor,and packings interposed between the electrodes and retainerswhereby the packings are tightened by centrifugal force and outwardpressure- 11. In apparatus for electrothermally treating materials, thecombination, with the furnace-body and its peripheral electrodes, of oneor more rings encircling the body and having collars admit-ting theelectrodes, insulation interposed between the furnace-body and rings,retainers for the electrodes at the ring-collars,and current-conveyingdevices in contact with said retainers.

12. In apparatus for electrothermally treating materials, thecombination, with the recessed electric furnace-body, and its peripheralelectrodes, of insulation in the body-recesses for the electrodes, oneor more rings encircling the body and having collars admitting theelectrodes, retainers for the electrodes at the collars, packingsinterposed between the electrodes and the retainers, andcurrent-conveying devices in contact with said retainers.

13. Apparatus for electrothermally treating materials, comprising arevoluble furnacebody, a refractory lining therein, a tubular fluid-bedwithin said lining constituting a common return electrode, andperipheral electrodes fitted in the body and lining and in contact withthe fluid-bed, whereby said bed is electrically energized for treatmentof material passing through it.

14;. Apparatus for electrothermally treating materials, provided withouter electrodes, an inner common electrode in circuit therewith, aninterior open-ended conduit of low electrical conductivity within theinner electrode, and a layer of carbon or equivalent material havingrelatively higher electrical conductivity within the interior conduit.

15. Apparatus for electrothermally treating materials, comprising arevoluble structure provided with outer peripheral electrodes, an innercommon electrode in circuit therewith, an interior conduit of lowelectrical conductivity within the inner electrode and a layer of carbonor equivalent material having relatively higher conductivity within theinterior conduit.

16. Apparatus for electrothermally treating materials, provided withouter electrodes, an inner common electrode in circuit therewith, and aninterior open-ended conduit of low electrical conductivity within theinner electrode and out of contact with the outer electrodes.

17. Apparatus for electrothermally treating materials, provided withouter electrodes, an inner common electrode in circuit therewith,

IIG

specification in the presence of two subscribing witnesses.

an interior open-ended conduit of low electrical conductivity Within theinner electrode and out of contact with the outer electrodes, I and alayer of carbon or equivalent material I 5 having relatively higherconductivity within Witnesses:

HUDSON MAXIM.

the interior conduit.

In testimony whereof I have signed this HENRY ASH, OsoAR E. LANGER.

